Papers by Keyword: Titanium Boride

Abstract: Particle size and distribution affect the thermal properties such as thermal conductivity, thermal expansion, and mechanical properties. In this study, TiB2 particles were used for the dispersant of pure aluminum composites because of high thermal conductivity and low thermal expansion of TiB2. Composites with different dispersibility and volume fraction of particles were prepared by spark plasma sintering. The effect of particle dispersibility in composites on thermal conductivity was estimated quantitatively by the simulation and experiments. As increasing dispersibility, the thermal conductivity was decreased and Vickers's hardness increased, but alternation for thermal conductivity was very small. With increasing volume fraction of particles, the effect of the particle dispersion on the change of the thermal conductivity increased. In addition, the empirical equation of the thermal conductivity considering dispersibility was estimated. The coefficient of thermal expansion decreased with increasing the particle volume fraction, and the experimental value quite accorded with a result provided by the rule of mixture.

Abstract: The work presents the thermodynamic calculations of the adiabatic combustion temperature and the fraction of the liquid titanium phase during the chemical reaction of the initial titanium and boron powders with the initial titanium content from 5 to 80 wt. % during the synthesis of materials based on TiB-Ti. It is shown that with an increase in the preheating temperature of the initial samples to 500 °C, the combustion temperature of the selected composition increases from 3200 to 3600 K, and the fraction of the liquid phase increases from 40 to 80 %. The peculiarity of molding composite materials based on TiB-Ti under conditions combining self-propagating high-temperature synthesis (SHS) and high-temperature shear deformation is studied. These conditions are realized in the method of free SHS compression, which allows synthesizing, molding and obtaining compact material in tens of seconds without using special molds. It was found that the maximum degree of deformation of the synthesized material corresponds to 20-40 wt. % free titanium. For the selected compositions, compact composite materials were obtained by free SHS compression method, the structural features were studied, and the density and porosity of the central and regional parts of the samples were measured.

Abstract: At present, structural materials capable of absorbing thermal neutrons are used for long-term, compacted storage of spent nuclear fuel. This is necessary to prevent the occurrence of a fission reaction in clusters of nuclear materials. A promising direction in this area is the use of neutron-absorbing coatings. In this paper, it is proposed to use coatings of the B-Ti system for this purpose. The model calculations carried out using the MCU-REA program show the sufficient effectiveness of such coatings. The average path length of the neutron in the coating is ~ 90 μm. The dependence of the degree of attenuation of the neutron flux on the thickness of the coating is shown. Calculations show that the main role is played not by the thickness of the coating, but by the boron concentration in the material. For the synthesis of coatings, the method of magnetron sputtering is considered. Аn experimental magnetron boron-containing target for a four-channel magnetron installation VUP-5M was fabricated.

Abstract: The improvement of thermal conductivity of tool steel is extremely important for order to achieve life prolongation of metal die used in die-casting. In order to improve the thermal conductivity without the degradation of mechanical properties, VGCF (vapor grown carbon fiber) and TiB₂ particles added in tool steel (SKD61) and to obtain the composites. Composites was fabricated by spark plasma sintering (SPS). Before sintering, SKD61 powders with 70μm in diameter and 1.9-3.8 vol. % VGCF with 0.15-0.2μm in diameter and 10-20μm in length or 4-8 vol. % TiB₂ particles with 2.62μm in average diameter was mixed by V shape type ball milling or planetary ball milling. Composites were sintered at 1273K with 50 MPa. The relative density of all composites is higher than 97%. The thermal conductivity improved from 20W/mK to 36W/mK by adding 8 vol. % TiB₂ particles, and to 25W/mK by adding 1.9 vol. % VGCF. On the other hand, the tensile strength of 1.9 vol. % VGCF/ SKD61 composites prepared under the condition of V shape type ball milling has 2200MPa. Composites with addition of 4vol. % TiB2 particles with V shape type ball milling and 1.9 vol. % VGCF with planetary ball milling is almost equal to the monolithic alloy. Good mechanical properties of the composites are caused by the grain refinement or interfacial strengthening by adding dispersants. But as increasing the contents of dispersants, the aggregation of the dispersants degrade the mechanical properties.

Abstract: Titanium alloy composites with titanium boride (TiB) discontinuous reinforcement have shown improved performance in terms of strength, stiffness, and hardness. Producing this composite through selective laser melting (SLM) can combine the advantages of freeform design with the ability to produce TiB reinforcement in-situ. In this study, SLM was used to consolidate a pre-alloyed Ti-6Al-4V (Ti64) and amorphous boron (B) powder mixture with the intent of producing 1.5wt% TiB reinforcement in a Ti64 matrix. The processing parameters of laser power and scanning speed were investigated for their effect on the density, microstructures, and hardness of the composite material. The results showed that the boron and Ti64 composite could achieve a density greater than 99.4%. Furthermore, it was found that processing parameters changed the microstructural features of the material. The higher the energy density employed the more homogenous the distribution of boron modified material. Macro features were also observed with laser paths being clearly evident in the subsurface microstructure. Micro-hardness testing and density measurement also showed a corresponding increase with increasing energy density. Maximum hardness of 392.4HV was achieved in the composite compared to 354.2HV in SLM fabricated Ti64.

Abstract: The present work reported a novel way of making nanocrystalline Ti-B phases (titanium boride and titanium diboride) in a hypersonic plasma jet. According to the purpose to synthesize nanosized Ti-B phases, experiments with different mass proportions of precursors were implemented. The optimal ratio of precursors, which leads to the yield of titanium diboride is 93.2% and the average particle size, doesn`t exceed 56.1 nm, is the ratio of Ti: B of 26.7: 73.3.

Abstract: TiO₂, B₂O₃, H₃BO₃, B₄C and carbon black were used as the raw materials to prepare TiB₂ powders by carbothermal reduction method. The influence of different content of carbon black (13.6~14.8 wt%) on products was discussed. The effects of different boron sources and holding time (10~50 min) on the microstructure of TiB₂ powders were also investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to study the phase composition and structural evolution of the powder. The final results showed that hexagonal TiB₂ crystal grain could be successfully synthesized without impurities when heated at 1700°C for 30 min in Ar atmosphere with the addition of 14.1 wt% carbon black. Submicrometric TiB₂ powders range from 0.5 to 1.0 μm could be obtained when B₄C was used as the boron source. The increase in holding time contributed to the grain growth and completion of chemical reactions, but could also result in oversintering.

Abstract: Structural investigations of the materials obtained by surface alloying with titanium-containing powder compositions using industrial electron acceleration were carried out. It was revealed that hardened particles of titanium carbides and borides were formed as a result of high-energy treatment. The highest value of materials studied microhardness was about 8.4 GPa. Friction testing against fixed abrasive particles showed that electron-beam cladding of the titanium and graphite mixture conduced to increasing material wear resistance by a factor of three.

Abstract: Conditions of electrodeposition, the structure and physical-mechanical properties (microhardness, base cohesion, internal stresses, corrosion currents) of nickel-based galvanic composition coatings with nano and micropowders of titanium boride are investigated. It is determined that electrocrystallization of nickel in the presence of boride nanoparticles leads to the formation of coatings with small-sized structural fragments, low porosity and increased physical-mechanical properties. Titanium nanoboride is simultaneously a component of the composition coating and an effective modifier of the nickel matrix. The presence of nanoboride in the electrolyte improves its performance by increasing the allowable upper limit of the cathode current density.

Abstract: The sliding friction behaviour of several ceramics, SiC,TiC,TiB₂ and their multiphase composite, had been studied under different humidity against Al₂O₃ ceramic ball. The results showed that, although the friction coefficients decreased along with humidity increased for all ceramics samples , the wear of ceramics had different performance. In high humidity condition, SiC can react with water in air to form oxide film enhance decreasing the wear. The wear rate of multiphase composite of SiC-TiC-TiB₂ are nearly not affect by humidity and are much smaller than for other ceramic.Key words: silicon carbide; titanium carbide; titanium boride; ceramic; oscillating sliding; humidity